Fluid brake systems are used on automobiles, trucks, and other vehicles. In such systems there are typically either brake shoes or brake calipers which engage a brake drum or brake disc. Brake drums and discs are subjected to high forces which cause distortion and resulting lack of cirularity. When this happens the brake shoes or discs are less able to effectively brake because they tend to hop or skip off of the high points of the distorted brake drum or disc.
It has been previously known that an accumulator or pressure equalizing device can be used for reducing pressure surges in hydraulic braking systems. Such devices also help to equalize the pressure experienced by each brake cylinder. U.S. Pat. No. 3,430,660 to Mitton shows a pressure equalizing apparatus. U.S. Pat. No. 4,571,009 to Jones, the current inventor, also shows another pressure equalizing apparatus. Both of these equalizers have a resilient bulb which is held within a housing. The bulb is contained within a concave cavity which allows the side walls of the bulb to flex outwardly when increased braking pressures are applied to the interior of the resilient bulb.
Both of these prior art brake system equalizers have been found by the inventor to suffer from response deficiencies. Under harder braking conditions high pressures are developed in the braking system. It has been discovered that such high braking pressures can cause the flexible bulb to fully expand within the chamber of the equalizer. This greatly reduces or effectively eliminates proper operation during extreme braking conditions. Attempts to increase high pressure responsiveness have lead to relatively poor response characteristics under medium and light braking conditions.
Light braking conditions have a substantial need for brake equalization and suppression of pressure waves developed due to brake eccentricities. Light braking becomes particularly important with respect to rain slickened and snow covered roads. Under these conditions the eccentricities of the braking components can have a dramatic effect on braking effectiveness because the forces developed between the roadway and wheel are reduced. The eccentricities can therefore more easily cause wheel lockup and the resulting skidding and loss of vehicle control.
The prior art brake equalizers have also suffered from difficulties associated with variations in brake systems from one type of vehicle to another. In some vehicles the addition of a brake system equalizer has caused undesired softness in the apparent braking force applied by the driver. The same or similar unit installed in another car might perform optimally. The utilization of a single type of brake system equalizer has thus been a compromise which provided less than optimum performance for at least some vehicles. Customization of brake equalizers has not been practical because of the lack of knowledge of the variable parameters causing the change and the increased costs in inventory, manufacturing and installation.
Thus there remains a substantial need in the art of fluid brake systems for an equalizer or accumulator which is appropriately responsive at low, medium and high braking pressures associated with varying operator pedal pressures and stopping requirements. There is also a continuing need for effective braking system equalization under varying road conditions which experience varying amounts of braking force developed between the wheel and road. There also remains a strong need for a pressure equalizing and wave suppressing accumulator which is suitable for use on a range of vehicle types and sizes.